This invention relates generally to microwavable utensils. More particularly, this invention relates to a closure device which permits the joining of two generic cooking vessels such as dishes or bowls together to form a microwavable cooking utensil.
Cooking in a microwave oven is popular because of its speed and efficiency. Many foods are more efficiently cooked by microwave when a lid covers the top of the food containing vessel. The lid traps air over the food reducing the amount of volume that has to be heated making the system more efficient. Certain foods such as vegetables may be better cooked with a small amount of water in the lower vessel. The microwave energy turns the water in the lower vessel to steam and the steam helps cook the vegetables. The lid formed by the upper vessel helps to trap the steam and cook the vegetables.
The vessels are best made from materials that are transparent to microwave energy because they will not become hot from that type of energy. However, microwavable cooking utensils can become hot by means of energy transfer such as conduction and convection arising from the food itself as it becomes hot.
The lid of a microwavable cooking utensil must not be so tightly applied that there is danger of explosion due to steam pressure created by heating the water vapor in the air trapped by the lid. For this reason lids of vessels used in microwave cooking are not so tightly sealed that excess pressure cannot vent to the atmosphere.
Fast microwave heating can result in unequal heating of food leaving part of the food cold and part hot. This problem is remedied by interrupting the cooking process and physically rotating the utensil holding the food within the microwave oven about its vertical axis so that the microwave energy is more evenly dispersed through the food mass.
Many users of microwave ovens use a clear thin plastic wrap over the top of bowls and utensils as a lid when cooking. This alternative when multiplied by millions of users can have a ecological impact because of the energy consumed in making the plastic and the final problem of disposing of it when it is no longer wanted.
The prior art has addressed some of the above stated problems. For example, a microwavable lid has been described in U.S. Pat. No. 4,847,459 issued to Desai. The Desai patent discloses a bowl shaped microwave dish with a cover which promotes the heating of food. The Desai arrangement requires the bottom portion of the vessel and the lid to conform to a custom design with certain interlocking offset steps molded into the lid and into the bottom dish which provide the restraint necessary to hold the lid in place during the cooking process while providing necessary venting.
The problem of the user handling hot utensils has been addressed by U.S. Pat. No. 4,033,009 issued to Hoinash which discloses removable handles that are applied to cooking vessels that have thin arcuate shaped handles. The handles described have thin arcuate shaped slots which slip over the arcuate handles of the dish or bowl. This solution is limited to those dishes which have the type of handle described and the disclosed slip on handle has no other purpose than to provide support and means to carry the hot dish without burning the user.
U.S. Pat. No. 4,158,464 issued to Bowen et al. shows a plastic collar that is placed around a restriction in a vessel with a silicone rubber pressure absorbing material between the plastic collar and the vessel the purpose of which is to protect the vessel and assure a firm fit of the collar. The collar so applied has means that allow the attachment of a removable handle to the collar for use in moving and manipulating the container.
U.S. Pat. No. 4,644,858 issued to Liotto et al. describes two semicircular rims of metal hinged at one point so that they can be closed around a flat circular base to form a pan. The described pan allows easy removal of the baked material from the pan.
While the devices of the prior art are effective for their particular purposes, they do not contemplate the joining of two generic vessels to form a bowl and lid. Moreover, in moving and rotating the devices described by the prior art and to protect the user from possibly coming in contact with a hot utensil, generally a removable handle of some type has been relied upon or has had to be supplied in conjunction with a device on the utensil. These separate items add further undesirable complication and cost for the user.